Display arrangement



June 12, 1951 Filed Oct. 2, 1947 G. T. BAKER 2,556,640

DISPLAY ARRANGEMENT 3 Sheets-Sheet l 1 65m 7 BAA-ER June 12, 19 1 G; T. BAKER 2,556,640

DISPLAY ARRANGEMENT F-Hmi on 2 M34? 3 She etsS heet 2 1 2 3 4 5 -6 7 8 9 O 103 v FG IN vE/vTaR 6-501: TBA/ran June 12, 1951 G. T. BAKER DISPLAY ARRANGEMENT 3 Sheets-Sheet 5 Filed Oct. 2, 1947 0am I USMC PCA .Z'N vs/vron Game: 7. BAKER Patented June 12, 1951 UNITED STATES" PATENT OFFICE DISPLAY ARRANGEMENT I George Thomas Baker, Liverpool, England, assignor to Automatic Telephone & Electric Company Limited, Liverpo company 01, England, a British Application October 2, 1947', Serial No. 777,487 In Great Britain November 6, 1946 The present invention relates to display arrangements and is more particularly concerned with display arrangements of the type disclosed plates, the variable voltages causing the spot to trace an-outline of the desired character on the, screen while the steady voltage which is fixed for any one character determines the position-of the centre of the character on the screen. By varying the steady voltage from character to character, successive characters may be caused to.

appear in sequence on the screen and by suitably predetermining the values of the steady voltage, the characters may be caused to appear on the screen in a prearranged formation. Each individual character willbe repeated at high speed while the complete trace will also be repeated continuously as long as the particular display is required.

It will be understood that a satisfactory display is most easily obtainable when using a screen having a longafterglow characteristic. However, it has been found that in such a case some interference .is visible due in part to the fact that the wipers of the uniselector which feed the voltages to the deflection plate cannot beadjusted to step absolutely simultaneously. It is lone of the objects of the present invention to avoid this defect. V

7 According, therefore, to one feature of the in vention, in a display arrangement employing a cathode ray tube associatedwith means for applying variable and steady voltages to the deflection plates of the tube to cause a number of characters to be displayed on the screen of the tube, switching means are provided for blacking out the screen during the inter-character traverse as well as during fly-back.

In one arrangement according to this feature of the invention the switching means consist of arelay associated with the cathode ray tube and adapted to be operated when a display is to be exhibited, the relay being controlled by the magnet of the uniselector which feeds the voltages to the deflection plates of the tube or tubes so that it releases when the wipers of the uniselector are being stepped from one position to the next and prevents the flow of beam current during movement of the wipers. H

5 Claims. (01.177933?) 2 The provision of a control of this nature may also be applied to enable a plurality of cathode ray tubes to be associated with common equipmentfor providing the variable and steady voltages to the deflection plates.

.According to this feature of the invention, in a displayarrangement employing a plurality of cathode ray tubes associated with means for ap-.

plying variable and steady voltages to the deflection plates of the tubes to cause a number of characters to be displayed on the screen of the tubes, the circuits which control the application of said voltages to the deflection plates are com-.

mon to a plurality of tubes and are arranged so as to applysaid voltages in parallel to the deflection plates of all. the tubes, switching meansv being provided "which control the blacking out of the screens of all tubeswhich are not required toexhibit a display.

According. toa further feature of the inven- A the circuits for controlling the application of the variable. and steady voltages to the deflection plates of the tubes are provided in common and serve to apply said voltages to the deflection plates of all the tubes, switching means being provided for causing the black-out 0f the screen of a tube exhibiting a display during the intercharacter traverse and for causing the complete black-out of the screens of the tubes which are not required to exhibit a display.

The invention finds particular application to telephone systems in which it is necessary to display before an operator information such as calling subscribers numbers, and according to a further feature of the invention, in a display arrangement for operators positions in telephone systems, each operators position is provided with a cathode ray tube and common equipment is provided for applying variable and steady voltages to the deflection plates of all the tubes to cause characters to be traced on the screens, the performance of a switching operation by anoperator serving to ensure that the voltages applied to the deflection plates of all the tubes are rendered effective only on that tube individual to the operators position.

. Itwill beappreciated that while the above arrangements have particular application to the display of a calling subscribers number which may for instance include four digits displayed side-by-side on the screen the invention is obviously applicable to provide a more extended display by the application of suitable shifting potentials to the plates of the cathode ray tube. Several lines of characters could thus be obtained depending only on the size of the characters relative to that of the. screen. The. controlling factor in an extended display of this type, however, is of course the writing speed and a reasonably. steady extended display would require a higher speed of operation of the figure generator which provides the varying voltages, applied to thong;- flection plates.

With such an increased speed, however, the=intor-character black-out control described above is not suitable and in this case the switching means comprise the interrupter contacts of. thefmag-net. of the uniselector which feeds the voltages o the deflection plates of the tube or tubes, the interrupter contacts being connected in series with the magnet and theprimary winding .of atransformer the. secondary. winding of whichv is. connected in. the. circuit of one. electrode. of the. cathode. ray tube in such amanner that the openingpf-theiirk. terrupter contacts causes a yoltage-surgeto be de; veloped. in said secondary.- winding andaappliedto said. electrode. to. prevent the flow of beam .cur-v rent.

The invention will be better understood from the following description of: one embodiment shown in the. accompanying drawings in which the. invention is applied to. display. arrangements. for operators positions vina telephne.system.. In the drawings Figs. 1 and 2. which-shouldbe arrangedgsidefbye side with Fig. l on. the left, show the. common equipment CE and. two operators position cir cu-itsPCA and 12GB while Fig. 3 shows an alternative circuit.for.the ap.-. plication of the blackeout potential tot-heicathode ray tubes.

Referring first to. Figs. 1 and 2, the. common. equipment CE comprisesa figure .generatorFG, figure selectorsDA, DB, DCand DD and a. layout, selector DS. The figure-generator. isdescribed in. detailin applicantsco-pendingUnitedStates.ape. plication Serial No. 750,142 and is-shown in diagramatic form only herein. Briefly itconsistsof. a motor I00 driving. a shaft I03= to. which a source of alterating currentv I0 I: is connected: by. means of brush I02. A number ofncapacitors-ai. provided in the figure. generator, each of which has two stationary plates anda movable plate, the movable plates for all the capacitors being mounted on the shaft I03 for rotation between the stationary plates. Thusthecapacitor I05 has a movable plate I04 fixed to the shaft I03, Alternating current connected to the shaft "13- is fed through the capacitors and rectified such as-by rectifier I06. The movable plates of the capacitors are not circular but arecut' to shapeasdescribed in the above-mentioned application in. such a manner that the varying voltage obtai'ned by rectification of the alternating current-serves when applied tothe deflection plates ofthe cathode ray tube to cause the cathode ray beam to trace-the outline of the appropriate characteron the screen. It will be understoodthat the varyingvoltages are available continuously and the application of the appropriate voltages to cause the display oi a desired sequenceof four characters is effected bythe setting ofthefour-figure selectors DA, DB, DC andDB.

The figure selectors comprise a uniselector for each character, four being used in the present case since the display is limited to four characters but it will be understood that any other number may be employed as desired. The figure selectors are controlled by incoming trains of impulses which are fed to a circuit of which only the impulse-repeating contact 1M]? and the changeover contacts TH, EU and TE. are shown. Each uniselector is provided with two wipers and associated bank contacts, the wipers being connected .to the bank contacts associated with wipers DSI and D83 of a further uniselector, the layout selector 119$, while thecoptacts are connected to the outputs of. the fignre generator. The necessity fortwowipers arises-from the fact that in general two varying .voltages are required for the generation of a character and the corresponding contacts, of the two banks of each uniselector are connected to the appropriate pair of outputs from the-figure generator, the wipers being connected to the X and Y plates through the layout selector DS. An exceptionto-this takes, place in the case of. the digit 1 whereobviously only one. varying:

otential will be, required. and this. will be applied, 7 to they Y plates. Contact: lof banks, DAL, DBI...

DCI and DDI. whichfeedthexplates are conse..-. quently disconnected.

The layout selector. 13S

varyin voltages. to the. X and Y plates as .de.-.

scribed above. While.- bankDSZ. serves to apply: a. steady voltage. to the plates of the. tube. inorder;

key KIA. When an operator requires a callin number to be. displayed, sheon rates the k y-K which. at contactsnot. shown. serves to initiate. identification and. transmission of identity. signals.

IlVIB, the. first. train beingaeffective on uniselector magnet DA so. thatthis uniselector is set.in ac.v

oordance with. thefirst train. At the end .of: the

first train changeover contact TH. operates and the next train is effective on magnetDB. Afterthis train contact HUoperates and the.;third train is effective on magnet DG-while thefourthtrain is effective on magnet DD on the operation of:

contact TE.

The operation of key KIA also i causes. the 0p eration of-relayl-lAover resistance YF- and=bothwindings of the relayzin series. Relay HA in operating short-circuits the high resistance righthand winding, therelay holding overits'low re sistance left-hand winding thereby applying; a guarding potential tolead- I 5 which prevents theoperation ofa relays-uch-as HBin-theevent that the key K'IBis operated at a-time when the commonequipment isin use.

Relay HA in'operating'at contacts HA2 causestheoperation of the pulsing: relay PU in series with the magnet interruptersprings-DSMG and; at-contacts HA3-prepares the circuit of relay-SGA which circuit iseempleted-at contacts PUZ on-the operation of relay PU. Relay-PU-in operatingat has. thr e banks. DSL. BS2 and D53 of whiChDSI and. DS 3. feed the" The impulses representing these signals; are repeated to the common equipment at contact,-

contacts PUI closes the circuit of the drive magnet DSM which energises and at interrupter springs DSMC opens the circuit of relay PU. Relay PU releases and opens the circuit of relay SGA and also the circuit for the drive magnet which thereupon releases and the wipers are stepped to position 2. The appropriate varying voltages are now fed over wipers DAI and DAZ of the figure selector DA, wipers DSI and D83 re-: spectively of the layout selector DS to the X and Y plates respectively of the cathode ray tube.

It will be noted that relay SCA is operated as long as the magnetv DSM is energised and is re- ;leased while the magnet is de-energised i. e. durthrough the tube. When relay SCA operates and the contact SCAI is opened, the modulating grid is connected through YG to a point in resistance YH so that the potential applied to the grid is more positive, the values of the resistances being so chosen that beam current now flows.

It will be understood that relay SCA will remain in its released condition for slightly longer than the time taken for the wipers to step from one position to the next since its circuit is dependent upon the operation of relay PU which is in turn operated upon the closure of the interrupter springs DSMC. Hence the steady D. C. bias will have been applied to the plate PXZ for an appreciable period before the beam current again begins to fiow so that the provision of the contact SCAI will black-out the screen for the duration of the inter-character traverse and also during the fiy-back period.

The alternative arrangement shown in Fig. 3 is intended for use in cases where a more extended display than the four digits of the calling partys number is required and where, in consequence, a higher writing speed is employed. Normally the full negative potential is applied to the modulating grid of the tube CRT over break springs HA3. When the common equipment is taken into use from one position, relay HA operates whereupon the modulating grid is connected via make springs of HA3, lead l6, high impedance secondary winding of transformer TRJA, lead [1, make springs HA4 to a tapping on resistance YP which with YQ forms a potentiometer across the supply voltage. The modulating grid is thus rendered less negative and beam current flows. The primary winding of the transformer TR-A consists of a few low resistance turns and the variable resistance YN is connected in parallel therewith. The primary winding is connected in series with the magnet DSM and the interrupter springs DSMC. The circuit is arranged so that as the interrupter springs DMC break to deenergise the magnet DM and step the wipers to the next position, the induced surge in the secondary winding renders the modulating grid negative to produce a momentary black-out. The duration of the black-out pulse may be varied by variation of the non-inductive resistance YN connected across the primary winding of the transformer.

With regard to the mounting of the cathode ray tube, in-particular Where it is employed at a demand operators position for providing the number of thecalling party, the tube may be mounted behind the front panel of a manual board. The screen will belargely concealed by an escutcheon plate and the number will be visible through a. recessin the front of the manual board, the cowl .thus formed providing a light screen. It willof course be-appreciated that a cathode ray tubehaving a small screen will usually. be used in these cases and a typical screen diameter will be four centimeters- Thecharacters produced will thenbe approximately three to four millimetershighand a full display of five digits will occupy lessthan an inch width.

An alternative mounting position .is in the desk of the manual position, the axis of. the tube lying immediately beneath and parallel to the. surface of the desk. Thenumber is read .by means of a mirror permanently fixed to the lid of thedesk and sunk well below thesurface. The recess is closed by a glass. sheet flush with thesurfaceand in this position the number is easily read since the tube is well screened fromdirect light.

A single power pack can be employed fora large number of tubes and would preferably be run from the mains with a standby vibrator unit for battery operation. High resistances are inserted at the source in all leads carrying high voltages so that contact with these leads cannot cause injury. In addition all wires are totally enclosed, the main run being in conduit and the final connection to the display in flexible metal tubing. The tube itself will preferably have a mu-metal screen, the whole sheathing being continuous and earthed.

I claim:

1. A character display arrangement comprising a cathode ray tube having a fluorescent screen, a grid electrode for controlling the flow of beam current in said tube and deflecting plates for said electron beam, means for producing a variable voltage and a steady voltage, a uniselector having a driving electromagnet and a plurality of wipers, means for feeding said variable and steady voltages over said wipers to said deflecting plates to enable characters to be traced in at least one row on said screen, a switching device operated by the release of said electromagnet to remove a blackout potential from said grid electrode and released by the operation of said electromagnet to apply said blackout potential to said grid electrode and means for delaying the operation of said switching device a predetermined time after the release of said electromagnet in order to black out the screen both during the inter-character traverse and fly-back periods.

2. A character display arrangement comprising a cathode ray tube having a fluorescent screen, a grid electrode for controlling the flow of beam current and deflecting means for the electron beam, means for producing a variable voltage and a steady voltage, stepping means for sequentially applying said variable and steady voltages to said deflecting means to cause the electron beam to trace the outline of a plurality of characters in' difierent positions on said screen, switching means responsive to the operation of said stepping means for generating a potential while said stepping means moves from one position to the next and means for applying said potential to said grid electrode to prevent the flow of beam current in said tube during said movement.

woman .3. A character display arrangement loompris :a icathode ray tube having :a fluorescent screen, a v grid electrode for controiling t'hjfiDW :of :beam :current and deflecting plates for the electron beam, means :for producing 2a variable voltage :and :a steady wolbage, "a nm'selector hav- Zing a driv'ing electromasgnet and :a plurality of wipers, means for feeding :said variable and Steady voltages over said wipers in successive positions to said adefieoting i'p'lates Zto enable cha iacters to fine tnaeed on said :screen, :a sswitching device aesponsive to the operation of :said dniving eleeiromagnet vior :genem fing a potential while said dniving electromagnetrstepssaid wipers ffrom -one position :to the .next and mieans'ifor applying Said :pdtential to said grid electrode to prevent, Ashe flow :of beam icurreni: in said tube during 'SBJid movement.

a. icharacte'r dismay arrangement as claimed in claim 3 wherein said switching devi'ce cinn- :pr-ises a srelay which .is operated only when a tube to exhibit :a display, :said 'neiay having a contact which in the unoperated position eonnects a source of negaxt'ive potential eto said grid electrode.

REFERENCES GITED T ne iol'iowing references are of record in one iihis atent:

UNITED STATES PATENTS 

